Analysts have yet to decide whether the weapon that flew over northern Japan shortly after dawn was also a failure as the missile reportedly broke into three parts before crashing into the Pacific Ocean.

Ten days later, the missile attracted analysts' attention when it was paraded through Pyongyang during celebrations to mark The Day of the Sun, the national holiday marking the anniversary of the birth of Kim Il-sung, the founder of the nation.

The Hwasong 12 is paraded across Kim Il Sung Square during a military parade in Pyongyang in AprilCredit:
AP

The following day, the second test ended in failure when a missile blew up within seconds of launch. A third test before the end of April also ended in failure.

In May, however, a Hwasong-12 was successfully launched from Kusong and reached an altitude of 1,310 miles and travelled around 490 miles before splashing down in the Sea of Japan.

"They have managed a successful lofted test flight, so a launch where they go for distance is a logical next step", said Lance Gatling, a defence analyst and president of Tokyo-based Nexial Research Inc.

"And to do that, they had no other geopolitical choice but to fly it over Japan", he told The Telegraph, given that neither China nor Russia would have taken kindly to a North Korean missile entering their airspace.

"Certainly it's a discourteous thing to do to a neighbour, but they apparently decided to go ahead in any case because they had no other choice if they wanted to test its range", Gatling said.

There may be an attempt to recover the missile, Gatling added, in order to determine more about its capabilities and whether it failed in flight or was destroyed on purpose in an effort to disguise its potential.

Analysts also point out that the missile could have caused casualties and damage if it had failed earlier in its flight and debris had fallen on Japan.

The liquid-fuelled, 52-foot missile is believed to be able to carry a nuclear warhead of up to 1,400 lbs and has a maximum range of 3,700 miles.

Seoul says the missile was launched from Sunan, which is where Pyongyang's international airport is, opening the possibility that North Korea launched a road-mobile missile from an airport runway.

Moon Seong Mook, a former South Korean military official and current analyst for the Seoul-based Korea Research Institute for National Strategy, said the airport's runways could provide the ideal space to launch a road-mobile missile like the Hwasong-12. By launching from its capital, the North might have been trying to demonstrate the ability to launch its missiles from anywhere, Moon told AP.

"The launch doubled as a threat to Washington, not only because of the US military bases in Japan, but also that the North showed it has the real capability to fire missiles to waters near Guam if it chose to shoot them in that direction," Moon said.